The separation of isotopes in the gas phase and, especially, uranium isotopes for uranium enrichment, based upon different molecular weights/or different kinetic cross sections of the molecules of the isotopes to be separated in the gas phase, can be effected by the separating-nozzle process well-documented in the literature and described in the aforementioned copending application, the art cited therein, the earlier application also mentioned above, and the publications identified below.
The gas mixture, in this system, is forced with or without a carrier (low-molecular-weight gas) through slit-like nozzles, the outflow of which is intercepted by skimmer-diaphragm arrangements which separate the molecules of heavier isotopes from those of the ligher isotopes.
The assembly of such nozzles and associated skimmer diaphragms are referred to hereinafter as separating-nozzle units or more generally, as separating units.
As described, inter alia, in the aforementioned copending application, it is common practice to feed each such separating-nozzle unit with a respective compressor and to connect the unit in cascade with other units for maximum resolution or separating efficiency.
The aforementioned applications, moreover, describe arrangements wherein at least part of the compression heat is removed from the gas by a cooler upstream of each unit.
Separating-nozzle units, their structural and operating principles and the various auxiliary device (compressors) used with these units are described in the following publications:
U.S. Pat. No. 3,362,131 PA1 U.S. Pat. No. 3,708,964 PA1 U.S. Pat. No. 3,877,892 PA1 German Pat. No. 1,052,955 PA1 German Pat. No. 1,096,875 PA1 German Pat. No. 1,198,328 PA1 German Pat. No. 1,794,274 PA1 German Pat. No. 2,031,687 PA1 German published application (Auslegeschrift) DT-AS No. 25 42 296 PA1 Chemie-Ingenieur-Technik, volume 29, pages 364 ff. (1977) PA1 Chemie-Ingenieur-Technik, volume 39, pages 1 ff. (1967) PA1 Atomwirtschaft/Atomtechnik, volume 13, pages 359 ff. (1968)
As described in the aforementioned applications, a plurality of separating-nozzle units can be functionally integrated into a separating cascade with the aid of a vacuum-type vessel having a circular-plan configuration (generally spherical in the latter application) and internally subdivided by radial partitions into sectors for the respective cascade stages.
The gas ducts can be arranged centrally in the sectors in the upper part of the vessel and as connecting passages between the compressors, the coolers and the central gap passages. The compressors may be mounted directly below the vessel.
Prior to this development and in most earlier applications of the process, the apparatus was functionally integrated into a separation cascade although the devices of the latter were usually not structurally integrated. The common practice was to provide the separating stages next to one another and to connect them with gas ducts which could be provided with enveloping or surrounding ducts (jackets) to limit the possibility of the escape of gas in the event of a failure in the system.
When a row of separate units was connected in cascade by such ducts, they had to be spaced widely to allow positioning of the compressors between them. As a result the apparatus needed long supply and feed lines for gas, cooling water etc. and was costly to construct and control.
Since all units and subassemblies of the apparatus had to be sealed vacuum tight against atmospheric pressure, the numerous failure-prone welded seams necessary to this end created problems and required high welding costs. All of these disadvantages were reflected in the high capital and operating costs of uranium enrichment of the separating-nozzle process.
While the system described in my above-mentioned application Ser. No. 725,493 (see German published application-Auslegeschrift-DT-AS No. 25 42 296 and U.S. Pat. No. 4,093,436) was free from the last mentioned group of disadvantages, work with this system has shown that it is capable of improvement. The system disclosed in my application Ser. No. 888,974, uses a generally spherical housing and is capable of providing simplification and improvement for systems having large gas throughputs which are to be processed.
The present invention is primarily concerned with an apparatus for uranium enrichment by the separating-nozzle process which thus comprises a plurality of separating-nozzle units as previously described, heat exchangers of the tube-bundle or, more particularly, of the tube-type upstream of the separating-nozzle units, compressors respectively associated with the separating-nozzle units and gas ducts for the supply of the starting gas and the functional integration of the separating-nozzle units into a separating cascade having a plurality of stages. With the system using an upright cylindrical configuration as just described, difficulties have been encountered with the orientation and disposition of the heat-exchanger sections. In general, the heat exchanger tubes in such constructions cannot be of the throughgoing type. It is difficult, moreover, in such systems to lead away and supply the coolant, generally water, to these heat exchangers.